Optical configurations in a tileable display apparatus

ABSTRACT

A display apparatus including a screen layer for displaying a unified image to a viewer and an illumination layer having an array of light sources. Each light source emits a light beam. An array of optical elements, each coupled to a corresponding light source in the array of light sources, is disposed between the screen layer and the illumination layer. The display layer includes a matrix of pixlets and a spacing region disposed between the pixlets in the matrix, wherein the array of light sources emit their light beams through the array of optical elements, wherein each optical element is configured to shape the received light beam into a divergent projection beam having a limited angular spread to project sub-images displayed by the pixlets as magnified sub-images on the backside of the screen layer, the magnified sub-images to combine to form the unified image that is substantially seamless.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. §119(e) to U.S.Provisional Application No. 61/856,462, filed 19 Jul. 2013. The contentsof the priority provisional application in their entirety areincorporated herein by reference.

TECHNICAL FIELD

This disclosure relates generally to displays, and in particular, butnot exclusively, relates to tileable displays.

BACKGROUND

Large displays can be prohibitively expensive because the cost tomanufacture display panels increases exponentially with display area.This exponential cost increase arises from the increased complexity oflarge single-panel displays, the decrease in yields associated withlarge displays (a greater number of components must be defect-free forlarge displays), and increased shipping, delivery, and setup costs.Tiling smaller display panels to form larger multi-panel displays canhelp reduce many of the costs associated with large single-paneldisplays.

Tiling multiple smaller, less expensive display panels together canresult in a large multi-panel display that can be used as a large walldisplay. The individual images displayed by each display panel canconstitute a sub-portion of the larger overall image collectivelydisplayed by the multi-panel display. While a multi-panel display canreduce costs, it has a major visual draw-back. Specifically, bezelregions that surround the displays put seams or cracks in the overallimage displayed by the multi-panel display. These seams are distractingto viewers and detract from the overall visual experience. Furthermore,when many high-resolution displays are used to make a large multi-paneldisplay, the overall image is extremely high resolution, which createsbandwidth and processing challenges for driving image content(especially video) to the extremely high resolution display.

BRIEF DESCRIPTION OF THE DRAWINGS

Non-limiting and non-exhaustive embodiments are described with referenceto the following figures, wherein like reference numerals refer to likeparts throughout the various views unless otherwise specified.

FIGS. 1A-1C are two perspective views and a cross-sectional view,respectively, of an embodiment of a display apparatus that includes adisplay layer disposed between a screen layer and an illumination layer.

FIG. 2 is a semi-transparent plan view of an embodiment of a displayapparatus looking through a screen layer to a display layer.

FIG. 3 shows an embodiment of a tiled display formed of more than onedisplay apparatus tiled together.

FIG. 4A is a cross-sectional view of an embodiment of a displayapparatus.

FIG. 4B is a cross-sectional view of another embodiment of a displayapparatus.

FIG. 5A is partial cross-sectional view of the embodiment of a displayapparatus of FIG. 4A illustrating its operation.

FIG. 5B is a partial cross-sectional view of an embodiment of a displayapparatus of FIG. 4A including a uniforming optical element.

FIG. 5C is an enlargement of the designated area in FIG. 5B.

FIG. 6A is a partial cross-sectional view of an embodiment of a displayapparatus of FIG. 4A including a uniforming optical element.

FIG. 6B is a cross-sectional view of an embodiment of a uniformingoptical element.

FIG. 7 is a partial cross-sectional view of another embodiment of adisplay apparatus.

FIG. 8 is a partial cross-sectional view of another embodiment of adisplay apparatus.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

Embodiments of an apparatus and a system of tileable displays aredescribed. In the following description, numerous specific details areset forth to provide a thorough understanding of the embodiments. Oneskilled in the relevant art will recognize, however, that the techniquesdescribed herein can be practiced without one or more of the specificdetails, or with other methods, components, materials, etc. In otherinstances, well-known structures, materials, or operations are not shownor described in detail to avoid obscuring certain aspects.

Reference throughout this specification to “one embodiment” or “anembodiment” means that a described feature, structure, or characteristicis included in at least one embodiment. Thus, appearances of the phrases“in one embodiment” or “in an embodiment” in this specification do notnecessarily all refer to the same embodiment. Furthermore, the describedfeatures, structures, or characteristics can be combined in any suitablemanner in one or more embodiments.

FIGS. 1A-1C illustrate an embodiment of a display apparatus 101 thatincludes a display layer 120 disposed between a screen layer 110 and anillumination layer 130. While FIGS. 1A-1C do not illustrate interveninglayers between the layers 110, 120, and 130, it should be appreciatedthat embodiments can include various intervening optical and structurallayers, such as lens arrays, optical offsets, and transparent substratesto provide mechanical rigidity.

FIG. 1A shows that illumination layer 130 includes an array of lightsources 131, 132, 133, 134, 135, and 136. Each light source in the arrayof light sources illuminates a corresponding pixlet to project thesub-image of the pixlet onto the screen layer 110 as a unified image. Inthe embodiment illustrated in FIG. 1A, each pixlet includes atransmissive pixel array with a plurality of individual transmissivedisplay pixels arranged in rows and columns (e.g., 100 pixels by 100pixels in one embodiment). Each pixlet displays a part of an overallimage and, when coupled with a light source and a screen as furtherdescribed below, projects a magnified version of its part of the overallimage onto the screen.

FIG. 1B also shows that illumination layer 130 includes light sources131, 132, 133, 134, 135, and 136 disposed on a common plane ofillumination layer 130. In one embodiment, each light source can be alaser, but in other embodiments, each light source can be alight-emitting-diode (“LED”) that emits light from a relatively smallemission aperture. Generally, the aperture size selected will depend ona tradeoff between brightness and resolution, taking into account thesize of the pixlet with which the light source is coupled. For example,LEDs with an emission aperture of 150-300 microns can be used in oneembodiment, but in other embodiments smaller emission apertures (e.g.,less than 150 microns) or larger aperture sizes (greater than 1 mmsquare, for example 1.1 mm in one particular embodiment) can be used.The LED can emit white light. In still other embodiments, othertechnologies can be used as light sources. In one embodiment, each lightsource is an aperture emitting light from a light integration cavityshared by at least one other light source.

Display layer 120 includes a matrix of pixlets 121, 122, 123, 124, 125,and 126. The illustrated embodiment is a 2×3 matrix of pixlets 121-126,but other display layers can have different numbers and/or arrangementsof pixlets. In the illustrated embodiment, each pixlet in the matrix ofpixlets is oriented on a common plane of display layer 120. The pixletscan be liquid-crystal-displays (“LCDs”) that can be color LCDs ormonochromatic LCDs. In one embodiment, each pixlet is an independentdisplay array separated from adjacent pixlets by spacing region 128. Inone embodiment, each pixlet measures 20×20 mm. The pitch between eachpixlet in the matrix can be the same. In other words, the distancebetween a center of one pixlet and the center of its adjacent pixletscan be the same distance. In the illustrated embodiment, each lightsource in the array of light sources has a one-to-one correspondencewith a pixlet. For example, light source 131 corresponds to pixlet 121,light source 132 corresponds to pixlet 122, light source 133 correspondsto pixlet 123, and so on. Also in the illustrated embodiment, each lightsource is centered under its respective corresponding pixlet.

Display layer 120 also includes spacing region 128 surrounding pixlets121-126. In FIG. 1B, pixlet 126 is adjacent to pixlets 123 and 125.Pixlet 126 is spaced by dimension 162 from pixlet 125 and spaced bydimension 164 from pixlet 123. Dimensions 162 and 164 can be considered“internal spacing” and need not be the same distance, but are the samein some embodiments. Pixlet 126 is also spaced by dimensions 161 and 163from edges of display layer 120. Dimensions 161 and 163 can beconsidered “external spacing” and need not be the same distance, bur arethe same in some embodiments. In one embodiment, dimensions 161 and 163are half of dimensions 162 and 164; in one example, dimensions 161 and163 are both 2 mm and dimensions 162 and 164 are both 4 mm. In theillustrated embodiment, the internal spacing between pixlets issubstantially greater than the pixel pitch (space between pixels) ofpixels included in each pixlet.

In the embodiment of FIG. 1B, the magnified sub-images would each be thesame size and be square-shaped. To generate same-sized magnifiedsub-images, in one embodiment display layer 120 and its pixlets 121-126can be offset from light sources 131-136 by a fixed dimension 165 (Inone embodiment, dimension 165 is 8 mm), but other embodiments caninclude the ability to adjust the spacing and angle between theillumination layer and display layer to adjust the magnification, andthus the size of the pixlet images, on the screen. This can compensatefor thickness variation in the pixlet-to-screen distance, for example.The illumination layer can also be adjusted laterally relative to thedisplay layer to align the edge of the image to the edge of the screenon each panel.

Spacing region 128 contains a backplane region that includes pixel logicfor driving the pixels in the pixlets. One potential advantage of thearchitecture of display apparatus 101 is increasing space for additionalcircuitry in the backplane region. In one embodiment, the backplaneregion is used for memory-in-pixel logic. Giving the pixels memory canallow each pixel to be refreshed individually instead of refreshing eachpixel in a row at every refresh interval (e.g., 60 frames per second).In one embodiment, the backplane region is used to assist in imagingprocessing. When display apparatus 101 is used in high-resolution largeformat displays, the additional image processing capacity can be usefulfor image signal processing, for example dividing an image intosub-images that are displayed by the pixlets. In another embodiment, thebackplane region is used to embed image sensors. In one embodiment, thebackplane region includes infrared image sensors for sensing 3D scenedata in the display apparatus' environment.

FIG. 1C illustrates a cross-section of display apparatus 101. Each lightsource 131-136 is configured to emit a divergent projection beam 147having a limited angular spread that is directed toward a specificcorresponding pixlet in display layer 120. In an embodiment, divergentprojection beam 147 can be substantially shaped as a cone (circularaperture) or an inverted pyramid (rectangle/square aperture). Additionaloptics can be disposed over each light source in the array of lightsources to define the limited angular spread (e.g., 20-70 degrees)and/or cross-sectional shape of divergent projection beam 147 emittedfrom the light sources. The additional optics (including refractiveand/or diffractive optics) can also increase brightness uniformity ofthe display light in divergent projection beam 147 so that the intensityof divergent projection beam 147 incident upon each pixel in a givenpixlet is substantially similar.

In some embodiments not illustrated in FIG. 1C, divergent projectionbeams 147 from different light sources can overlap upon the spacingregion 128 on the backside of display layer 120. In some embodiments,each pixlet is directly illuminated solely by one divergent projectionbeam from its corresponding light source, which can approximate a pointsource. In certain embodiments, a very small percentage of light fromnon-corresponding light sources can become indirectly incident upon apixlet due to unabsorbed reflections of divergent projection beams 147from the non-corresponding light sources. Spacing regions 128 andillumination layer 130 can be coated with light absorption coatings todecrease reflections from non-corresponding light sources fromeventually becoming incident upon a pixlet that does not correspond withthe light source. The limited angular spread of the light sources can bedesigned to ensure that divergent projection beams 147 only directlyilluminates the pixlet that corresponds to a particular light source. Incontrast, conventional LCD technology utilizes lamps (e.g., LEDs orcold-cathode-fluorescents) with a generally Lambertian lightdistribution and diffusive filters in an attempt to generate uniform anddiffuse light for backlighting an LCD panel.

In operation, display light in a divergent projection beam 147 from alight source (e.g., light source 131) propagates toward itscorresponding pixlet (e.g., pixlet 121). Each pixlet drives its pixelsto display a sub-image on the pixlet so the display light thatpropagates through the pixlet includes the sub-image displayed by thepixlet. Since the light source generates the divergent projection beam147 from a small aperture and the divergent projection beam 147 has alimited angular spread, the sub-image in the display light gets largeras it gets further away from the pixlet. Therefore, when the displaylight (including the sub-image) encounters screen layer 110, a magnifiedversion of the sub-image is projected onto a backside of screen layer110.

Screen layer 110 is offset from pixlets 121-126 by a fixed distance 166to allow the sub-images to become larger as the display light (indivergent projection beams 147) propagates further from the pixlet thatdrove the sub-image. Therefore, fixed distance 166 can be one componentof how large the magnification of the sub-images is. In one embodiment,fixed distance 166 is 2 mm. In one embodiment, each sub-image generatedby pixlets 121-126 is magnified by 1.5×. In some embodiments eachsub-image generated by each pixlets 121-126 is magnified by 1.05-1.25×.The offset by fixed distance 166 can be achieved by using a transparentintermediary (e.g., glass or plastic layers).

In one embodiment, screen layer 110 is fabricated of a matte materialsuitable for rear projection that is coated onto a transparent substratethat provides the offset by fixed distance 166. The backside of screenlayer 110 is opposite a viewing side 112 of screen layer 110. Screenlayer 110 can be made of a diffusion screen that presents the unifiedimage on the viewing side 112 of screen layer 110 by scattering thedisplay light in the divergent projection beams 147 (that includes thesub-images) from each of the pixlets 121-126. Screen layer 110 can besimilar to those used in rear-projection systems.

FIG. 2 shows a semi-transparent plan view of an embodiment of a displayapparatus 101 looking through screen layer 110 to display layer 120.Display apparatus 101 can generate a unified image 193 using magnifiedsub-images 192 generated by light sources 131-136 and theircorresponding pixlets 121-126. In FIG. 2, pixlet 124 generates asub-image 191 that is projected (using the display light in thedivergent projection beam 147 from light source 134) onto screen layer110 as magnified sub-image 192. Although not illustrated, each pixlet121, 122, 123, 125, and 126 can also project a magnified sub-image ontoscreen layer 110 that is the same size as magnified sub-image 192. Thesefive magnified sub-images, combined with magnified sub-image 192, formunified image 193. And because the geometric alignment of the magnifiedsub-images would leave virtually no gap (if any) between the magnifiedsub-images, unified image 193 will be perceived as seamless by a viewer.The magnified sub-images on the backside of the screen layer 110 combinelaterally to form unified image 193. Magnification of the sub-imagesallows the unified image to reach the edge of screen layer 110, whiledisplay layer 120 and illumination layer 130 can still include amechanical bezel that offers rigidity and support for electricalconnections, but that is out of sight to a viewer of display apparatus101.

FIG. 3 shows a pair of display apparatuses 101 and 301 tiled together toform an embodiment of a tiled display 300. Tiled display 300 displays anoverall image that is a combination of a unified image (e.g., unifiedimage 193) projected by display apparatus 101 and a unified imageprojected by display apparatus 301. In the illustrated embodiment,display apparatus 301 is substantially the same as display apparatus101, but different reference numbers are used for discussion. Displayapparatus 101 can be tiled together with other display apparatuses in amodular approach to building tiled display 300. In one embodiment, aself-healing adhesive is applied between screen layer 110 and screenlayer 310. This adhesive will blend screen layer 110 and screen layer310 to hide easily perceived seams between screen layers 110 and 310 intiled display 300. In one embodiment, the self-healing adhesive is madeof polymers. In another embodiment, a monolithic screen layer isdisposed over display layer 120 and 320 so that the screen layer doesnot have a seam. Monolithic screen layers with appropriate mechanicalfixtures can be sized to common tiled arrangements of multiple displayapparatus 101 (e.g., 2×2, 3×3, 4×4). Third and fourth display apparatusthat are the same as display apparatus 101 could be added to tileddisplay 300 to form a larger tiled display that is a 2×2 matrix ofdisplay apparatus 101 and that the larger display could have the samepotential advantages as explained in association with tiled display 300.Of course, displays larger than a 2×2 matrix can also be formed.

In FIG. 3, dimension 167 is the same distance as dimension 162. Thismaintains the pitch between pixlets 126 and 324, as illustrated, andensures that the edge of the magnified sub-image generated by lightsource 334 and pixlet 324 geometrically aligns with the edge of themagnified sub-image generated by light source 136 and pixlet 126.Similarly, the edge of the magnified sub-image generated by light source331 and pixlet 321 geometrically aligns with the edge of the magnifiedsub-image generated by light source 133 and pixlet 123. In this way, theunified image projected on screen layer 310 aligns with the unifiedimage projected on screen layer 110 to form the overall image displayedby tiled display 300.

Because the magnified sub-images, and therefore the unified images, ofdisplay apparatuses 101 and 301 are aligned at their edges on screenlayer 110/310, the pixel pitch and density of the overall image canremain the same, even where display apparatuses 101 and 301 are coupledtogether. Hence, where traditional tiled displays have a distractingbezel where two display layers are coupled together, tiled display 300can have an unperceivable seam because of the near-seamless visualintegration of the unified images as the overall image on tiled display300.

In some embodiments (not shown), mechanical structures can be added toeach display apparatus 101 to facilitate the correct physical alignmentof additional display apparatus. In one embodiment, electricalconnectors that facilitate power and image signals are included indisplay apparatus 101 to facilitate modular construction of a tileddisplay using the display apparatus 101.

FIG. 4A illustrates an embodiment of a display apparatus 400. Displayapparatus 400 is in most respects similar to display apparatus 101 shownin FIG. 1C. In some embodiments of a display apparatus it can bedesirable to include optical elements that condition the light emittedby the light sources before it is incident on the pixlets on the imaginglayer. The primary difference between display apparatuses 101 and 400 isthat display apparatus 400 includes optical elements 402 that areoptically coupled to light sources 131, 132, and 133 so that light fromeach of light sources 131-133 passes through a corresponding opticalelement on the way to corresponding pixlets 121-123. In the illustratedembodiment there is a one-to-one correspondence between light sources anoptical elements.

Optical elements 402 can be refractive, or diffractive optical elementsand can have positive or negative optical power, so that they cancollimate, focus, or otherwise alter the light beams emitted by lightsources 131-133. Although illustrated as a single element, in anotherembodiment each optical element 402 can be a compound optical elementmade up of multiple subelements. In some embodiments the compoundmultiple subelements can be of the same type (refractive, diffractive,etc.), but in other embodiments the multiple subelements can be ofdifferent types—that is, the compound optical element can combinerefractive and diffractive subelements, refractive subelements, and soon.

Each optical element 402 is positioned on illumination layer 130 and issupported above its corresponding light source by a structure 404. Inone embodiment, structure 404 can be a ring-like structure thatsurrounds the light source and supports optical element 402 in thecorrect position above its corresponding light source. In otherembodiments structure 404 need not completely surround its correspondinglight source. In embodiments where structure 404 does surround itscorresponding light source, the structure can be opaque to preventcross-contamination of light sources—that is, to prevent light from onelight source from straying, directly or indirectly, to a pixlet thatcorresponds to another light source.

In different embodiments, the light sources can be different types ofsources including light emitting diodes (LEDs), small-aperture LEDs,lasers, fiber optics, and so on. In the illustrated embodiment, eachlight source 131, 132, and 133 is a light-emitting-diode (“LED”) thatemits light from a relatively small emission aperture. For example, LEDswith an emission aperture of 150-300 microns may be used. The LEDs canemit white display light in one embodiment, but blue LEDs, ultraviolet(UV) LEDs, or other LEDs of a different color/wavelength can be used inother embodiments. Each lamp 131, 132, and 133 is configured to emit alight beam toward its respective optical element 402. Optical elements402 then define the limited angular spread of the light beams emittedfrom the lamps, and can also increase brightness uniformity of thedisplay light propagating toward the pixlets. In some embodiments, forexample, the intensity uniformity can be ±10 percent and the angularspread β (see FIG. 5A) can be limited to 45 degrees or 30 degrees.

FIG. 4B illustrates an embodiment of a display apparatus 450. Displayapparatus 450 is in most respects similar to display apparatus 400:optical elements 402 are optically coupled to corresponding lightsources 131, 132, or 133, and there is a one-to-one correspondencebetween light sources and optical elements. Optical elements 402 canhave positive or negative optical power, such that they can collimate,focus, or otherwise alter the light beams emitted by corresponding lightsource 131-133, and can be refractive or diffractive, or some compoundoptical element. The primary difference between optical apparatuses 400and 450 is that in display apparatus 450 optical elements 402 arepositioned on a separate optical layer 452. Optical layer 452 ispositioned between illumination layer 130 and display layer 120, so thatlight beams from light sources 131-133 pass through correspondingoptical elements 402 on the way to their corresponding pixlets 121-123.In one embodiment, optical layer 452 can include interstitial spaces 454between optical elements 402. In some embodiments, interstitial spaces454 can be coated with a light-absorbing coating, such as black paint inone embodiment, to prevent reflection of light between layers that couldcause light cross-contamination. As in display apparatus 400, indifferent embodiments the light sources can be of various kinds.

FIG. 5A is partial cross-section of display apparatus 400 illustratingits operation. The operation described is of a single lightsource/optical element/pixlet/screen combination, but other of thesecombinations on the display apparatus function similarly. Duringoperation, light beams are emitted by light source 131 and pass throughoptical element 204. Optical element 204 applies its optical power, aswell as its other optical characteristics, to condition the light beamoutput by light source 131 into divergent projection beam 147. Divergentprojection beam 147 has a spread angle β, measured from the optical axisof optical element 402, such that the edge-to-edge spread angle of thedivergent projection beam 147 is 2β. By appropriate design of the shapeand optical characteristics of optical elements 402, the magnitude of βcan be tightly controlled. The magnitude of β is generally determined byfactors such as the size of the pixlet 121 to which optical element 402is optically coupled, as well as the distance between optical elementand pixlet. In some embodiments, it can be desirable for the magnitudeof β to be such that all light in the divergent projection beam 147 isincident on the corresponding pixlet. In various embodiments, β canrange from 0 degrees to 90 degrees, and in some embodiments from 0degrees to 30 degrees or 0 degrees to 45 degrees.

FIGS. 5B-5C illustrate additional aspects of the operation of displayapparatus 400. Generally there is a correlation between the aperturesize of the light source in the resolution of the image: a smallersource generally produces a sharper image. As shown in FIG. 5C, for goodresolution it can be useful to adjust the size of the light source sothat the local divergence of the light—that is, the angle γ subtended atthe display pixels by the light source—is small. In one embodiment, forexample, γ can be 6 degrees or less, but in other embodiments it can besmaller, for example 1.7 degrees or less in one particular embodiment,and in still other embodiments it can be larger.

FIGS. 6A-6B illustrate an embodiment of a display apparatus 600. Displayapparatus 600 is in most respects similar to display apparatus 400. Theprimary difference between display apparatuses 400 and 600 is thatdisplay apparatus 600 includes a uniforming optical element 602—that is,an optical element designed to provide uniform illumination of itscorresponding pixlet. Without uniforming optical element 602, light atthe edges of pixlet 121 would be dimmer compared to the center due tothree factors: the incident angle on the screen, the apparent size ofthe source as seen from this angle and the increased distance to thescreen. Uniforming optical element 602 makes illumination of pixlet 121more uniform by having the center of optical element 602 collect a smallcone of rays from light source 131 spread it out to a larger cone, asillustrated with rays 604. Likewise, at or near its edges opticalelement 602 can take a large cone of rays at a high angle and bend itinward to make it smaller, as illustrated with rays 606. Putdifferently, optical element 602 is designed to apply negative opticalpower near its center and positive optical power near its edges.

FIG. 6B illustrates an embodiment of a refractive uniforming opticalelement 602 that can be used in display apparatus 600. The illustratedembodiment is substantially cylindrical in shape and has a substantiallyflat first surface S1 that will be in contact with the light sourceaperture and a second surface S2 whose z coordinates are defined by theequation:

$z = {\frac{{cr}^{2}}{1 + \sqrt{1 - {\left( {1 + k} \right)c^{2}r^{2}}}} + {\sum\limits_{i = 1}^{N}\; {\alpha_{i}\rho^{i}}}}$

where r²=x²+y², ρ=r, and c is the curvature of surface S2, defined asc=1/R where R is the radius of surface S2, and k and αi arecoefficients. In one particular embodiment, the values of thecoefficients k and αi are given in the following table:

Surface Coefficient S1 S2 C 0 0.13429898 K 0 0 α1 0 α2 0.010499324 α3−0.046097216 α4 −4.6210965E−3   α5 3.1405504E−4 α6 1.8297661E−4 α73.3705639E−6 α8 9.8246009E−6 α9 −2.271147E−6

FIG. 7 illustrates a partial cross-section of an embodiment of a displayapparatus 700. Display apparatus 700 is similar in many respects todisplay apparatus 400. The primary difference between displayapparatuses 400 and 700 is the light source. Display apparatus 700 usesa laser 704 as a light source. Laser 704 is positioned on illuminationlayer 130 and is side-coupled to optical element 702. In the illustratedembodiment, optical element 702 is a diffractive optical elementconfigured to couple laser light in on the edge and distribute it to beemitted from the diffractive optic, parallel ±0.5% to an optical axis ofthe diffractive optic, and then continuously and incrementally largerangles with linear variation to the edge of the optic, where it emergeson the right and left sides at its largest angle β (e.g., 45 degrees)with a local divergence of 0.5 degrees. In one embodiment, a diffractiveoptical element 702 can be obtained from Ergophos LLC, but otherdiffractive optics can also be used. Having local-low-divergence displaylight from the light sources (e.g., 0.5 degrees) can be helpful inmaintaining image integrity in sub-images that are projected onto screenlayer 110. In other embodiments, different types of lasers and differentoptical elements can be used and, moreover, they can be opticallycoupled differently than shown and described. For example, in oneembodiment the optical element need not be diffractive and the laserneed not be side-coupled to the optical element.

FIG. 8 illustrates an embodiment of a display apparatus 800. Displayapparatus 800 is similar in many respects to display apparatus 400. Theprimary difference between display apparatuses 400 and 800 is thatdisplay apparatus 800 uses optical fibers 804, 806, and 808 as lightsources on the illumination layer. One end of each optical fiber ispositioned in illumination layer 130, oriented to emit a light beam fromits fiber core toward its corresponding optical element 402 and itscorresponding pixlet, while the other end of each fiber is coupled to alight source 802. In operation, light is injected into each opticalfiber by light source 802. Light travels through each optical fiberuntil it reaches the fiber end, where it is emitted as a beam from thefiber core toward optical elements 402 and the corresponding pixlet. Inother embodiments, optical fibers 804, 806, 808 need not use the samelight source 802, but can instead use different light sources.

The above descriptions of embodiments of the invention, including whatis described in the abstract, is not intended to be exhaustive or tolimit the invention to the disclosed forms. Specific embodiments of, andexamples for, the invention are described herein for illustrativepurposes, but various modifications are possible within the scope of theinvention, as those skilled in the relevant art will recognize.

These modifications can be made to the invention in light of the abovedetailed description. The terms used in the claims that follow shouldnot be interpreted to limit the invention to the specific embodimentsdisclosed in the specification. Rather, the scope of the inventionshould be determined entirely by the following claims, construed inaccordance with established legal doctrines of claim interpretation.

1. A display apparatus comprising: a screen layer for displaying aunified image to a viewer on a viewing side of the screen layer that isopposite a backside of the screen layer; an illumination layer having anarray of light sources, wherein each light source emits a light beam; anarray of optical elements, each optical element optically coupled to acorresponding light source in the array of light sources; a displaylayer disposed between the screen layer and the illumination layer, thedisplay layer comprising: a matrix of pixlets, and a spacing regiondisposed between the pixlets in the matrix, wherein the array of lightsources are positioned to emit their light beams through the array ofoptical elements, wherein each optical element is configured to shapethe received light beam into a divergent projection beam having alimited angular spread to project sub-images displayed by the pixlets asmagnified sub-images on the backside of the screen layer, the magnifiedsub-images to combine to form the unified image that is substantiallyseamless.
 2. The display apparatus of claim 1 wherein the array ofoptical elements comprises a plurality of optical elements positioned onthe illumination layer.
 3. The display apparatus of claim 1 wherein thearray of optical elements comprises a plurality of optical elementspositioned on an optical layer between the illumination layer and thedisplay layer.
 4. The display apparatus of claim 1 wherein the opticalelements have optical power.
 5. The display apparatus of claim 4 whereinthe optical elements are diffractive or refractive.
 6. The displayapparatus of claim 1 wherein the divergent projection beam has aselected spread angle.
 7. The display apparatus of claim 6 wherein theselected spread angle is from 30 degrees to 45 degrees.
 8. The displayapparatus of claim 1 wherein the optical element is a uniforming opticalelement that creates a beam of substantially uniform intensity incidenton the corresponding pixlet.
 9. The display apparatus of claim 8 whereinthe local divergence is less than 0.5 degrees.
 10. The display apparatusof claim 1 wherein the light sources are optical fibers with one endpositioned on the lighting layer and another end coupled to a lightsource.
 11. The display apparatus of claim 1 wherein each light sourceis a laser.
 12. The display apparatus of claim 11 wherein each laser iscoupled to a diffractive optical element.
 13. The display apparatus ofclaim 1 wherein each light source is a light-emitting diode (LED). 14.The display apparatus of claim 13 wherein each LED is a small-apertureLED.
 15. A multi-panel display comprising: a plurality of tileabledisplays arranged to form the multi-panel display, each tileable displaycomprising: a screen layer for displaying a unified image to a viewer ona viewing side of the screen layer that is opposite a backside of thescreen layer; an illumination layer having an array of light sources,wherein each light source emits a light beam; an array of opticalelements, each optical element optically coupled to a correspondinglight source in the array of light sources; and a display layer disposedbetween the screen layer and the illumination layer, the display layercomprising: a matrix of pixlets, a spacing region disposed between thepixlets in the matrix, and a spacing region disposed between the pixletsin the matrix, wherein the array of light sources are positioned to emittheir light beams through the array of optical elements, wherein eachoptical element is configured to shape the received light beam into adivergent projection beam having a limited angular spread to projectsub-images displayed by the pixlets as magnified sub-images on thebackside of the screen layer, the magnified sub-images to combine toform the unified image that is substantially seamless, wherein theunified images from each tileable display combine to form an overallimage displayed by the multi-panel display.
 16. The multi-panel displayof claim 15 wherein the array of optical elements comprises a pluralityof optical elements positioned on the illumination layer.
 17. Themulti-panel display of claim 15 wherein the array of optical elementscomprises a plurality of optical elements positioned on an optical layerbetween the illumination layer and the display layer.
 18. Themulti-panel display of claim 15 wherein the optical elements haveoptical power.
 19. The multi-panel display of claim 18 wherein theoptical elements are diffractive or refractive.
 20. The multi-paneldisplay of claim 15 wherein the divergent projection beam has a selectedspread angle.
 21. The multi-panel display of claim 15 wherein theoptical element is a uniforming optical element that creates a beam ofsubstantially uniform intensity incident on the corresponding pixlet.22. The multi-panel display of claim 1 wherein the light sources areoptical fibers with one end positioned on the lighting layer and anotherend coupled to a light source.
 23. The multi-panel display of claim 15wherein each light source is a laser.
 24. The multi-panel display ofclaim 23 wherein each laser is coupled to a diffractive optical element.25. The multi-panel display of claim 15 wherein each light source is alight-emitting diode (LED).
 26. The multi-panel display of claim 25wherein each LED is a small-aperture LED.
 27. A display apparatuscomprising: a screen layer for displaying a unified image to a viewer ona viewing side of the screen layer that is opposite a backside of thescreen layer; an illumination layer having an array of light sources,wherein each light source in the array is configured to emit a divergentprojection beam having a limited angular spread; and a display layerdisposed between the screen layer and the illumination layer, thedisplay layer comprising: a matrix of pixlets; and a spacing regiondisposed between the pixlets in the matrix, wherein the array of lightsources are positioned to emit the divergent projection beams havinglimited angular spread to project sub-images displayed by the pixlets asmagnified sub-images on the backside of the screen layer, the magnifiedsub-images to combine to form the unified image that is substantiallyseamless.
 28. The display apparatus of claim 27, further comprising anarray of optical elements, each optical element optically coupled to acorresponding light source in the array of light sources, wherein thearray of light sources are positioned to emit their light beams throughthe array of optical elements, wherein the optical elements areconfigured to shape the received light beam into the divergentprojection beams.
 29. The display apparatus of claim 28 wherein thearray of optical elements comprises a plurality of optical elementspositioned on the illumination layer.
 30. The display apparatus of claim28 wherein the array of optical elements comprises a plurality ofoptical elements positioned on an optical layer between the illuminationlayer and the display layer.